The present invention relates to the production of coated abrasives and particularly to the production of coated abrasives with a paper backing and more specifically to waterproof coated abrasives.
Such materials typically comprise a paper backing with the grain held by phenolic-modifed varnish resin maker and size coats. The use of the modified varnish as the bond renders the product waterproof. However it is found that such products require several hours to complete the cure of the binders and this therefore implies a very large inventory of "goods-in-progress" An alternative water-proofing treatment involves the use of a latex rubber saturant for the paper substrate.
It has therefore been proposed to use radiation-curable resin binders in place of the conventional phenolic resin-modified varnishes. Unfortunately the use of UV-radiation as the cure mechanism can not be applied from the backing side. In addition the UV radiation has very limited penetration and if the paper is highly filled, (as is often the case), the grains cast a UV shadow and the cure can be non-uniform. Faster cures may be obtained using electron beam radiation which is much more penetrating. Unfortunately such exposure tends to degrade the paper, leading to a product with reduced internal strength and integrity.
A waterproof paper-backed abrasive product has now been developed which has outstanding water resistance, flexibility and abrasive performance and yet can be produced with a cure time measured in seconds rather than hours or even minutes.